1. Field of the Invention
The present invention relates to a liquid crystal display (LCD) and, more particularly, to a reflective plate used in the LCD and a method for making the same.
2. Description of the Prior Art
Liquid crystal display (LCD) devices have recently undergone development to enable increases in size and improvements in definition while decreasing power dissipation. For these and other reasons, the LCD device has a most promising future.
Generally, there are two basic types of LCDs: a light transmissive type and a light reflective type.
The light transmissive LCD comprises a backlight disposed on a rear side of a liquid crystal cell. The light radiated from the backlight selectively passes through a liquid crystal, thereby realizing desired images.
The light reflective LCD comprises a reflective plate disposed on a rear side of the liquid crystal cell so as to reflect incident light toward the front side of the LCD cell, thereby realizing desired images.
The present invention is directed to the light reflective LCD, which will be referred to as a "reflective LCD."
FIG. 1 shows a conventional reflective LCD.
The conventional reflective LCD comprises upper and lower substrates 2 and 4. ITO electrode patterns 10 and 10' are disposed on opposing inner surfaces of the upper and lower substrates 2 and 4, respectively. Insulating layers 12 and 12' and orientation layers 14 and 14' are disposed on the ITO electrode patterns 10 and 10', respectively. Disposed between the lower substrate 4 and the ITO electrode pattern 10' are a reflective layer 6 and a first diffuser layer 8. Disposed between the orientation layers 14 and 14' is a liquid crystal layer 16.
A polarizer layer 18 and a second diffuser layer 20 are in this order disposed on an outer surface of the upper substrate 2. A retardation film may be further disposed on the outer or inner surface of the upper substrate 2 in case of an STN-LCD.
In the above described reflective LCD, only 50% of outer light introduced into the LCD as linear polarization by the polarizer layer 18 can be used to display an image. That is, the conventional reflective LCD has a drawback of a low light efficiency.
To solve the above drawback, Japanese laid-open Patents No. 92-243226 and 97-258219 disclose reflective LCDs having a reflective plate which can improve light efficiency. The reflective plate is shown in FIG. 2 and is designated by the reference numeral 64.
The reflective plate 64 comprises a substrate 40, an unevenly-surfaced layer 60 formed on the substrate 40, and a reflective layer 62 deposited on and unevenly-surfaced by the unevenly-surfaced layer 60. To form the unevenly surfaced layer 60, a photoresist resin layer is first deposited on the substrate 40, then patterned using a photo-mask, thereby obtaining an uneven surface. The photoresist pattern is hardened through a heat-treatment process, then the reflective layer 62 is deposited on the substrate to cover the photoresist pattern.
However, in the reflective plate 64, since the uneven surface of the reflective layer is formed in a uniform pattern as the same is formed through the photo-etching process, luminance may deteriorate by an interference of reflecting light.
In addition, to form the photosensitive pattern, additional devices such as a light exposure system and a mask, and additional processes such as an etching process are required. This increases manufacturing costs and complicates the manufacturing process.